Illuminating device for uniformly and diffusely illuminating a background



Nov. 14, 1950 R. F. E. STEGEMAN 2,530,133

nwumnmc DEVICE FOR UNIFORILY AND DIFFUSELY nwumnmc A mcxcnouun Filed June 8, 1946 RAYMOND F.E.STEGEMAN Z'Snvcntor zmmh Gttorueg Patented Nov. 14, 1950 UNITED STAT ES PATENT OFFICE ILLUMINATING DEVICE FOR UNIFORMLY AND DIFFUSELY ILLUMINATING A BACK- GROUND Raymond F. E. Stegeman, Greece, N. Y., assignor to Bausch & Lomb Optical Company, Rochester, N. Y., a corporation of New York Application June 8, 1946, Serial No. 675,373

4 Claims. (Cl. Mil-51.11)

the background in the present device is most nearly exemplified by the illumination of an integrating sphere in which a source of light when placed at the surface of the sphere uniformly illuminates the entire inner surface thereof. By way of comparison, the sphere in the present device is extended into a cylinder and substantially only half of the cylinder is utilized while the light source is linear and is positioned in alignment with and coextensive with the edge of the semicylinder.

It is an object of the present invention to provide a novel device of the above character for uniformly illuminating a background.

It is another object to provide such a device by utilizing principles similar to those used in illuminating an integrating sphere whereby a semicylinder is substituted for the sphere and an extended light source is substituted for the point source of light. I

It is a further object to provide such a device in the form of an optical testing apparatus wherein opaque characters are displayed in silhouette before a uniformly lighted background.

It is another object to provide such a device wherein the test characters may be quickly interchanged.

It is still a further object to provide such a device having means for controlling. and directing light rays emanating from the source of light.

Further objects and advantages will be apparent to those killed in this art from the following description and accompanying drawing in which:

Fig. 1 is a front elevation of a device embodying my invention,

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1,

Fig. 3 is a horizontal sectional view of another embodiment of the invention,

Fig. 4 is a fragmentary side elevation of the dimming device for the illuminating lamps,

Fig. 5 is a cross section taken on the line 5-5 of Fig. 4 showing the light-occluding shutter in open position, and l Fig. 6 is a cross section taken on the line 6-6 of Fig. 4.

In Fig. 1 of the drawing a cabinet I of any preferred form is provided with mean for displaying opaque characters, said means being in the form of a transparent display panel 2 of material such as sheet glass or clear plastic extending across the front wall 3. A framework 4 is attached by any suitable means to the cabinet l to furnish slots 5 to receive the transparent panel 2. The panel is so fitted within the slots 6 that it can be easily withdrawn when it is necessary to interchange the panels. The panel 2 has the opaque characters 6 formed thereon in any desired pattern, such, for instance, as found in optical testing charts, and by any suitable process such as photographically forming the characters on the surface of the panel 2 or adhesively securing them to it.

' According to the present invention, means for uniformly and diffusely illuminatinga background behind the characters 6 are provided in the form of a concave semicylindrical surface 6 of approximately a half circle in angular extent having along one of its longitudinal edges an extended diffuse light source in the form of a fluorescent tubular lamp II. The lamp II is so located with reference to the edge i2 that the through the longitudinal axis of the lamp. An

- in the form of an optical testing apparatus analogy to the relative arrangement of the background surface 9 with the lamp Ii, here shown. is'found in the arrangement of the corresponding elements in the integrating sphere; the surface of the sphere being uniformly illuminated by a source of light placed at its spherical surface. By way of comparing'the present device with the integrating sphere, the semicylinder in the present device is substituted for the sphere while the source of light is converted into an elongated tube having the same relative location to the surface as before. Therefore, the light incident on the background surface 9 has the same uniform illuminating effect as the light in an integrating sphere. For the' purpose of reducing reflection to a minimum, means are provided for obtaining a dull white appearance on the background surface 9 by suitably roughening and coating it with a dull white paint.

The light shields l3 and M are provided so as to confine the light emanating from the lamp llv to the angle subtended by the background. These light shields may be formed in any desired manner, but as here shown are designed asa part of the structure of the frame 4. Lamp H is 'positioned within the cabinet I by the brackets'i 5 and I6 and is connected to a suitable source of power which is controlled by switch ll.

In the embodiment of the invention shown in Fig. 3 a cabinet 20 is providedwith two circular semicylindrical walls 2| and 22. Along the longitudinal inner boundaries 23, 24-, and 25 of the walls 2| and 22, tubular fluorescent lamps 26, 21,

and 28 are located in the same relation to the is used. The lamp 2'! serves equally well for the two backgrounds 2| and and could be used without the lamps 26 and" and still obtain the same kind of uniform illumination. It will be understood that the lamps 20, 2,1, and 28 are connected through transformers and suitable switching apparatus to a source of electrical power, not shown.

In Fig. 3 themeans for producing a lightdiffusing dull white surface on the backgrounds 2i and 22 is in the form of overlying white sheets 29 and 3| of plastic-material suitably roughened to scatter the incident light. The sheets 29 and ii are principally retained in concave form against the background walls 21 and 22 by the recesses 32, 33, 34, and 35 carried by the boundaries 23, 24, and 25 of walls 2| and 22.

A front wall 39 is provided for the cabinet 20 in which apertures 37 and 38 are formed to define the lighted areas. A pair of transparent panels 39 and II are mounted in the wall 36 by a pair of frames 42 and 43 which have slots 44 and 45 to receive the panels 39 and 4|. In a manner similar to that disclosed in the first embodiment of the invention, characters of any desired pattern may be placed on the panels 29 and 4| to form charts for optical testing or otherwise. The outer edges of the frames 42 and H are provided with up-turned flanges II and 41 to form light shields similar to the light shields I3 and ll of Fig. 1.

If only one lamp 21 is used in the cabinet 20, the lamp and'its accompanying transformer 48 may be placed together in a casing 49 which can be easily removed for servicing. Suitable means such as spring detents or hooks, not shown, may be used to hold the casing 49 in an opening II in the front wall 36 of the casing 20. The casing 49 is provided with integral projecting walls 52 and 53 acting as light shields to restrict the light rays from the lamp 21 to the vicinity of the backgrounds 29 and 31.

Means for variably dimming the lamps shown in Figs. 1, 2, and 3, without altering the transverse distribution of the light with respect to'the backgrounds illuminated thereby are provided as shown in Figures 4', 5, and 6 by a li ht shutter generally illustrated at 54. The shutter is composed of an inner tube 55 closely surrounding a tubular lamp 58 and an outer tube 51 slidably telescoped over the inner tube. Both the inner and outer tubes are provided with transverse s ots 58 and 59, respectively, extending approximately half way around the circumference of the tubes and are axially located so that the slots 58 and 59 may be brought into registry by relative endwise movement of the tubes and 51. Since the tubes 55 and 51 are restrained from relative rotation, only relative endwise motion is used to vary the intensity of light emanating from the lamp 58.

Although but certain embodiments have been shown and described in detail, it will be understood that other embodiments are possible and that changes may be made in the form and arrangement of the parts without departing from the spirit of the invention as defined in the appended claims.

I claim:

1. In a device of the class described, means for providing a substantially uniformly and diffusely illuminated background comprising an elongated, concave, semi-circular light-diffusing surface of substantially 180 of angular extent, an elongated source of diffuse light rays extendaxis of the surface and coextensive therewith,

said source being positioned along one edge of the surface with the center of the source located substantially at the intersection of the plane of the diameter of the circle and said surface, and shield means partially surrounding the source for confining the light rays to the angle subtended by the surface. l

3. In a device of the class described, means for providing a substantially uniformly and diffusely illuminated background comprising a concave semicylindrical light-diffusing surface of approximately of angular extent, and tubular fluorescent lamps l ated with theaxes there-- of extending along th longitudinal inner edges of said cylindrical surfaces at the same identical radius as said surfaces; 0. white sheet of roughened plastic material closely held against said cylindrical surface to provide a dull surface thereon, and seating abutments at the edges of said surfaces for retaining said plastic sheet in concave form against said cylindrical surface.

' 4. In a'device of the class described, means for providing a substantially uniformly illuminated background comprising. a concave substantially semicylindrical light-diffusing surface, a tubular fluorescent lamp extending along and coextensive with a longitudinal edge of said semicylindrical surface in such a manner that said edge longitudinally bisects said lamp, and means for variably dimming the light rays emanating from said lamp, said means including a pair of telescoping tubes slidably mounted on the lamp for longitudlnal relative movement, said tubes being provided with registerable transverse open slots evenly disposed across said longitudinal edge whereby the intensity of illumination on said surface may be varied.

RAYMOND F. E. STEGEMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,005,898 Btahl Oct. 17, 1911 1,153,443 Pole Sept. 14, 1915 1,413,507 Turner Apr. 18, 1922 1,761,238 Scott June 3, 1930 1,900,551 Guth Mar. 7, 1933 2,254,718 Welch Sept. 2, 1941 2,305,892 Newman Dec. 22, 1942 2,308,988 Livers Jan. 19, 1943 2,335,951 Mansell Dec. 7, 1943 2,365,342 Hilliard et al. Dec. 19, 1944 FOREIGN PATENTS Number Country Date 270,184 Q Germany Feb. 10, 1914 709,505 France May 18, 1931 455,049 England Oct. 12, 1938 

